Press Brake Bending Calculator
Instantly calculate bending force, internal radius, minimum flange and V-die opening. Supports mild steel, stainless steel, aluminum and high-strength steel.
F = (1.42 × Rm × S² × L) / (V × 1000) [kN]
Ri ≈ V × 0.156 | Bmin ≈ V / 2 + S
How to Calculate Press Brake Bending Parameters
Bending Force Formula (DIN Standard)
F = 1.54 × Rm × S² × L / (V × 1000) [kN]
- F — Bending force (kN)
- Rm — Material tensile strength (MPa): S235=360, S275=430, SS304=700, AL=210
- S — Sheet thickness (mm)
- L — Bend length (mm)
- V — V-die opening (mm), optimal = 8×S
| Thickness (S) | V-Die (V) | Force (kN) | Force (tons) | Ri (mm) | B min (mm) |
|---|---|---|---|---|---|
| 1 mm | 8 mm | 132 kN | 13.5 T | 1.0 | 5.2 |
| 2 mm | 16 mm | 331 kN | 33.7 T | 2.0 | 10.5 |
| 3 mm | 24 mm | 496 kN | 50.6 T | 3.0 | 15.7 |
| 4 mm | 32 mm | 661 kN | 67.4 T | 4.0 | 21.0 |
| 6 mm | 48 mm | 992 kN | 101 T | 6.0 | 31.5 |
| 8 mm | 64 mm | 1323 kN | 135 T | 8.0 | 42.0 |
| 10 mm | 80 mm | 1654 kN | 169 T | 10.0 | 52.5 |
What is the optimal V-die opening for press brake bending?
The optimal V-die is 8× the material thickness for mild steel, stainless steel and aluminum. For high-strength steel (Weldox/Strenx 700+), use 12–13×. Example: 3mm mild steel → 24mm V-die. Too small a die increases force and cracking risk; too large gives an oversized radius.
How is internal bending radius (Ri) determined?
In air bending: Ri = V × k, where k is material-specific: mild steel 0.125, stainless 304 0.175, aluminum 0.10, high-strength steel 0.20. The internal radius is not controlled by the punch tip — it's determined by the V-die width and material springback.
What is the minimum flange length in press brake bending?
B = V × 0.656. The sheet must extend far enough to rest on both die shoulders. For a 24mm V-die: B = 15.7mm minimum. Bending with a shorter flange causes the sheet to slip into the die and produces inaccurate angles.
Air bending vs coining: which needs more force?
Coining requires 3–5× more force than air bending. Air bending is the standard method for most CNC press brakes — the punch does not bottom out and angle is controlled by depth. Coining bottoms the punch into the die for high repeatability but demands significantly more machine tonnage.
How much force does stainless steel require vs mild steel?
Stainless steel 304 (Rm 700 MPa) requires approximately 63% more force than mild steel S275 (Rm 430 MPa) for the same thickness, length, and die. For example: 2mm × 2000mm with 16mm V-die — mild steel 331 kN vs stainless 539 kN. Plan for a machine with at least 1.7× the tonnage you'd use for mild steel.
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